Nonlinear and quantum photonics using integrated optical materials

Integrated nonlinear photonics provides transformative capabilities for controlling, enhancing and manipulating material nonlinearities in miniaturized on-chip platforms. The extreme reduction of optical mode areas within subwavelength waveguides allows for large enhancements of light–matter interactions resulting in nonlinear phenomena at significantly lower optical powers than their fibre and free-space counterparts. The integration of nonlinear materials into nanophotonics has been instrumental in the practical implementation of emerging applications such as quantum information processing, high-speed optical communications, ultraprecise frequency metrology and spectroscopy. Since the early 2000s, the development of new fabrication methods combined with nanoscale design has led to tremendous improvements in the quality and integration capability of both traditional and new nonlinear material platforms. In this Review, we outline design principles to harness the potential of nonlinear materials on integrated platforms through improvements in waveguide loss, resonator design and dispersion engineering principles. We discuss how these tools have been used towards realizing several of the major goals of integrated nonlinear photonics such as broadband frequency conversion, frequency-comb generation, quantum light sources and nonlinear optical quantum logic gates. Nonlinear optical interactions can be substantially enhanced by the wavelength-scale confinement in integrated photonics, providing transformative capabilities for controlling, enhancing and manipulating material nonlinearities in miniaturized platforms. In this Review, we outline the design principles that harness the potential of nonlinear optical materials on integrated platforms and their utility in applications including broadband frequency conversion, frequency-comb generation, quantum light sources and nonlinear optical quantum logic gates.